Although the invention will be described in connection with certain embodiments it is not limited to those particular embodiments. On the contrary, the invention is intended to cover all alternatives, modifications and equivalent arrangements as may be included within the spirit and scope of the invention as defined by the appended claims.
Many wireless systems today, for example, those used in WiMAX and Long Term Evolution (LTE), provide nomadic and mobile radio connectivity. These wireless standards are designed for use in cases where the base stations (BTS) are stationary or fixed and they may use directional and omnidirectional antennas. In these systems, subscriber stations (SS) or client devices are primarily designed for use with omnidirectional antennas.
In addition, these wireless protocols are designed primarily for use in licensed frequency bands of operation where high Effective Radiated Power (EIRP) levels are allowed so longer communication ranges are feasible even when low gain omnidirectional antennas are used. These types of wireless protocols do not offer any special treatment of client devices that may use directional antenna systems neither provide any special ways how to address mobility of such devices.
In today's wireless landscape there are many different frequency bands allocated by national agencies around the world which are allowed for unlicensed operation, but the allowed Effective Isotropic Radiated Power (EIRP) in those bands is significantly lower, typically around 36 dBm. These bands can offer, in many cases, excellent performance for a number of wireless applications that require nomadic and mobile modes of operation, but due to the reduced link communication range network performance suffers greatly and applications are limited.
For these systems, one way to overcome these problems is by utilizing highly directive antennas to improve link radio frequency (RF) system gain, hence leading to increased link communication range while allowing the system to stay within EIRP limits. A salient feature of the wireless communication systems that use highly directive antennas is better performance in interference congested environments, which are typical for unlicensed bands of operation. This is because using directive antennas which are pointed to the desired source of the RF signal, leads to reduction of crosstalk from undesired RF emissions belonging to other users sharing the same spectrum, which leads to better signal to noise ratios (SNR) and better RF link performance.
Long range communications using high directivity RF antennas require accurate positioning and adjustment of the antenna azimuth and elevation. In nomadic and mobile applications, use of highly directive fixed antennas is almost impossible, since this would require continuous trained operator involvement to readjust and tune antenna alignment whenever the position of the network nodes changes.
Any attempt to enable this functionality in large points to multipoint networks using current systems requires continuous end user intervention. This is time consuming and obviously not feasible. There is a need for a solution that allows usage of highly directive antennas by a large number of network nodes in an automated and reliable fashion. This system must be able to create and maintain wireless links while stationary or mobile in a fast and reliable way by changing or pointing antenna beams in the direction of desired RF network nodes.
While there are other products in the marketplace that implement automatic antenna pointing controller units and use a variety of the algorithms to optimize antenna position in order to maximize performance, these systems have drawbacks.
One drawback is lack of scalability, as these solutions are used in point-to-point systems. This makes it difficult for use in a point-to-multipoint system.
Another drawback is that these systems are often not part of an integrated radio design. Typically these solutions use external hardware controller units and software to control mostly motorized antenna positioners. The interaction of the radio unit used in the link and hardware controller is through separate physical link interfaces such as Serial Peripheral Interface (SPI), Universal Serial Bus (USB), or Ethernet connections. This is a drawback as it introduces added cost, more cabling and less reliable solutions in real deployments.
A further drawback is that these systems suffer from latency in making decisions for optimum antenna position. This is because the only possible way for these systems to interact with generic radio links is by constantly polling for status information from the radio in order to obtain needed radio statistics information, for example, received signal strength indicator (RSSI) readings.
Another drawback is that these systems suffer from loss of throughput due to the overhead of sending extensive messages required to perform continuous antenna alignment. Messages sent over the air are really sent form one external controller to another external controller hence they contain application layer overhead such as, for example, IP header, Ethernet headers and so on.
Furthermore, these systems require additional hardware which introduces significant cost. Another drawback is that additional hardware occupies more real estate on the antenna tower and mast systems, increases loading and requires more complicated deployment and installations.